Be more gcc like in the way we deal with libgcc so that sh3/hppa millicode
and exception handling have a chance of working properly.
- creates libgcc, libgcc_eh and libgcc_s
- updates LIBGCC_SPEC to use them appropriately.
There's a hack in here at the moment with respect to libgcc_so in that it
is preferable to link against libgcc_so will only when -shared-libgcc is
specified (the c++ frontend does this automatically.) Configurations where
LINK_EH_SPEC is defined already do this. The gcc configuration for
NetBSD/alpha and another NetBSD platform (I forget which) actually define
LINK_EH_SPEC probably by accident rather than design.
- updates share/mk to use the compiler's knowledge of what needs linking into
libraries and executables. This removes an hppa hack.
- updates the sets for the newly created libgcc* files.
- support for linking against the _pg version of libgcc has been removed.